Rectifier



April 4, 1939. sc us 2,153,434

RECTIFIER Filed NOV. 15, 1934 Invenfi JfiZ/Tt F. Sin/minus,

: 7mm x/a s.

Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE Application November 15, 1934, Serial No. 753,139

4 Claims.

The invention relates particularly to rectifiers of the dry surface contact type and to a process of making same, and the general aim of the invention is to provide a device of this character possessing high rectifying efilciency and durability.

Another object is to provide a rectifier structure which is simple, compact and may be cheaply manufactured for sale at a relatively low cost.

A further object is to provide a rectifier which embodies an electropositive electrode formed from a metal, such as aluminum or magnesium, having electropositive characteristics and plated or surface-coated with a second metal, such as manganese, a compound of which with a mem-- ber of the oxygen series of the sixth periodic group, for instance sulphur, possesses rectifying characteristics.

Another object is to provide a novel process for producing a rectifier unit of this nature.

Other objects and advantages will become apparent in the following description and from the accompanying drawing, in which:

Figure 1 is a side elevation of a device embodying the features of the invention, part of the device being shown in longitudinal section.

Fig. 2 is a face view of a coated electropositive element, the coating being partially broken away.

Figs. 3 and 4 are transverse sections through an assembled cell before-and after forming respectively.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

A rectifier embodying the features of the present invention appears to function either according to the asymmetric conductivity principles of crystals or of intimate metal and metal-compound union somewhat similar to the so-called copper oxide rectifiers. In the present invention, however different metals are employed and the intimate, permanent union between the electropositive metal and the electronegative metalcompound is produced by subjecting the properly prepared and assembled couple to the presumably electro-chemical action of a forming current. A permanent layer is thereby produced which functions apparently on an electronic rather than an electrolytic principle.

Generally the foregoing results may be attained by following the steps of the process hereinafter particularly disclosed. One of the lighter electropositive metallic elements, for example aluminum or magnesium in the form of a relatively thin sheet, is provided with .a thin, uniform, hard or impervious film or coating of a different and generally heavier metallic element. This element should be one which forms a compound with a member of the oxygen family of the sixth periodic group (oxygen, sulphur, selenium and tellurium) having asymmetric conductive properties. Manganese is preferably used as the coating metal with sulphur as the combining element, since the compound (primarily manganese sulphide) resulting when these materials are used is a hard, dense and substantially indestructible compound. I

Considering aluminum as the electropositive metal, a sheet thereof is cleaned and a uniform film of metallic manganese is suitably deposited thereon preferably by an electrolytic deposition process. The depositing process may be performed upon the aluminum pieces in their final form but preferably a large sheet is coated and the individual elements fashioned subsequently. If before subjecting the sheet to the plating step but one side is cleaned to remove the oxides therefrom only the clean surface will become plated with managanese. Otherwise the manganese film must be subsequently removed from one side of the element.

An electronegative electrode element is fashioned from copper sulphide, the cuprous or hemisulphide, being preferred. Pure powdered cuprous sulphide is, by means of a press, formed into a, densely compacted slug, the shape and dimensions of which may vary as desired. However, the slug is usually a. fiat relatively thin disk conforming to the shape of the electropositive electrode element but slightly smaller in surface area.

The aluminum element and the cuprous sulphide slug are placed together with the manganese film contacting the face of the slu the elements are placed under pressure, and an alternating forming current of relatively high ina rectifier of whatever capacity and characteristics are desired. Instead of forming the couples individually, assembly ,thereof into final form may first be done and the complete rectifier then formed.

If the elements of a couple, after formation, are separated, it is found that the appearance of the manganese film on the electro-positive aluminum element haschanged radically. Instead of a green, smooth film, a silvery layer having an uneven or irregular surface is present. Presumably this layer consists of the sulphide of manganese but it is probable that it also contains aluminum and copper in sulphide form. Whatever its chemical composition may be, the layer is hard, permanent and intimately joined, as though fused, to the aluminum sheet. This combination appears to be the actual seat of the asymmetric conductivity since rectification is obtained with or without the cuprous sulphide slug.

} However, the separation of the aluminum and electrical contact under pressure with the exposed face, of the formed sulphide coating without rupturing the coating on the aluminum plate.

In the drawing an assembled rectifier structure and separate parts of a couple are shown in illustration of'the invention. The numeral l (Pig. 2) designates an electropositive element of aluminum having an electrolytically deposited film or coating of metallic manganese I l thereon. This element is, in this instance, in the form of a fiat circular disk. Assembled therewith, as shown in Fig. 3, is .a cuprous sulphide slug I2 of similar shape but of smaller surface area. After forming, and upon separation of the element l0 and slug l2, the silvery, uneven layer l3 (Fig. 4) is present between the contacting surfaces. This layer is apparently integral with the aluminum plate and the surface of the slug is quite uneven, as shown at ll, indicating a transformation and conversion of a portion thereof.

The rectifier device shown in Fig. 1 constitutes a simple, compact and effective structure which may be quickly and efficiently assembled. Two stacks l5 are formed containing preferably equal numbers of rectifying couples, each couple being separated from adjoining ones by a contact and heat radiating plate l6 of lead coated steel or like material. These stacks are placed between spaced bridge members I! which are connected by a single bolt I8 centrally disposed to extend between the stacks 15.

Between each end plate It and the bridge associated therewith is a massive disk l9 constituting pressure distributing and equalizing members. The elements, plates l6, and disks may be centrally apertured to receive a soft insulating cylinder l9, such as a wound mica tube, for maintaining alinement during assembly. Preferably portions of the bridges opposite the centers of the disks are struck toward the disks, as indicated at 20, to engage the apertures in the disks l9, this arrangement serving to insure transmission of pressure to the centers of the disks. The bridges preferably have outstanding flanges 2| along their" longitudinal sides to insure com- Centrally the bolt i8 is preferably insulated by a sleeve 23 of fibre or the like and outside the bridges I1 is encircled by inner insulating sleeves 23" and outer metal bushings 24 which are insulated from the bridges by washers 25 and provide seats against which nuts ,26 on the bolt may bear to apply pressure to the stacks of couples. The nuts may also serve to secure suitable mounting means, such as the brackets 21 to the unit.

The number of couples in each stack, the

arrangement of the stacks in similar or reverse It will be evident from the foregoing that an asymmetrically conductive cell of novel inherent characteristics has been provided by a new process for assembly in a unit of improved construction. The device has an eflicient output capacity, will not fail when subjected to high break-down voltages, and will withstand long usage. The units may be produced by the process quickly, economically and with uniformity of the required characteristics. The rectifier structure physically is sturdy and economical to produce and manufacture. All of these factors result in the provision of a highly satisfactory commercial product which may be manufactured and sold at a relatively low cost.

I claim as my invention:

1. A dry surface contact rectifier comprising, in combination, a pair of stacks of rectifying couples arranged side by side, an elongated bridge member extending from one stack to the other at each end thereof, a central insulated securing device extending between said bridges and adapted to exert pressure through said bridges upon said stacks, and disks interposed between the ends of said stacks and said bridges and having engagement with said bridges only over central portions of said disks.

2. A dry surface contact rectifier comprising, in combination, a pair of similar stacks of rectifying couples having contact plates between adjoining couples, a relatively heavy disk at each end of said stacks, said couples and plates and disks being centrally apertured, alining insulated means extending through said apertures, and means for supporting said stacks in side by side relation under operative pressure including bridge elements extending from one stack to the other at each end and having means thereon engageable with the aperture in said disks, and means between said stacks for securing said bridges together to apply pressure to said stacks.

3. A dry surface contact rectifying device comprising, in combination, similar stacks of rectifying couples, end plates on said stacks having central openings therein, bridge members adapted to extend across the ends of said stacks when placed side by side in slightly spaced relation, dome shaped bosses on the ends of said bridge members pressing into said openings, and a central bolt extending from one bridge member to by side in slightly spaced relation, a bolt extending between said stacks and through and beyond each bridge member, an insulating sleeve on the central portion of said bolt between said members, a pressure applying bushing mounted on each end of said bolt adjacent to said members and insulated from said bolt and associated member, and means on said bolt and bearing 5 against said bushings for applying pressure to said stacks through said bridge members.

KURT E. s. 

